Heretofore, inner seal assemblies have been provided for ram-type blowout preventers on oilfield drilling equipment for sealing the annulus about a tubular member such as a drill pipe. A blowout preventer normally has two opposed ram blocks mounted for inward movement toward each other for sealing engagement with the pipe. Each ram block has a packer formed of an elastomeric or hard rubber material for engaging the outer periphery of the pipe with the packers deforming against the pipe to form a tight seal. Each packer has a semicircular opening or recess to receive the pipe and form a tight seal with 180.degree. of the outer periphery of the pipe. Examples of such blowout preventers are shown in U.S. Pat. Nos. 1,695,992 dated Dec. 18, 1928 and 3,272,222 dated Sep. 13, 1966.
During a stripping operation, the drill pipe is pulled from the well bore with the blowout preventer in sealing relation against the drill pipe and frictional contact between the blowout preventer and the pipe being removed may result in considerable wear against the seal. For that reason, a wear insert may be added to the packer for contacting the pipe. For example, as shown in U.S. Pat. No. 4,398,729 dated Aug. 16, 1983, a semicircular insert is provided formed of a suitable resilient material which may include a nylon and/or urethane material. Such a semicircular insert is received within a recess in the packer and is urged against the elastomeric packer when contacting the drill pipe under substantial fluid pressure from the ram. The insert illustrated in U.S. Pat. No. 4,398,729 includes a pair of integral outwardly extending projections which are received within corresponding grooves for mounting of the insert within the packer. The resilient insert is depressed inwardly when initially inserted within the grooves to provide yieldable cooperation between the insert and the packer.
Screws or nails have also been utilized heretofore for retaining the insert in position within the elastomeric packer. However, upon closing of the ram and rotation of the drill pipe, the screws or nails tend to strip out of the elastomeric packer and if the fasteners are stripped from the elastomeric packer, the insert will spin or rotate with the drill pipe.